A new study published in the journal Alzheimer's and Dementia links high cholesterol with a lower risk of cognitive decline for people over 85 years old. But that might not necessarily mean that having high cholesterol prevents dementia.

The study authors compared the cognitive function of people in different age groups. By analyzing existing data from the Framingham Heart Study, they evaluated the cholesterol levels of Framingham subjects at different ages. "Midlife" cholesterol was recorded at around 40 years old while "late-life" cholesterol was recorded at around 75.

They were surprised to find that for people aged 85 to 94 years old, having higher late-life than midlife cholesterol was correlated with a 32 percent lower risk of cognitive decline. In other words, higher cholesterol among the very old was associated with a reduced chance for dementia.

The results for people 10 years younger, however, looked much different. Study participants aged 75 to 84 years old with higher late-life cholesterol texperienced a 50 percent higher risk of cognitive decline.

What do scientists make of these seemingly contradictory results?

Jeremy Silverman, lead author of the study, posits that the correlations are a result of the "protected survivor model." This model suggests that those who are protected, perhaps genetically (though scientists aren't sure), against the potentially harmful effects of high cholesterol on cognition are more likely to live into very old age - past 85 years old - and are disproportionately represented in that oldest population.

If you're worried about cholesterol, stop stressing about eggs and start eating more almonds. A recent study from Pennsylvania State University confirmed that eating just a few almonds per day can increase the good cholesterol, called HDL, in your body. The almonds also influence the body to transport...

(Holly Van Hare)

"Most people prior to late old age are vulnerable to the deleterious effects of total cholesterol," Silverman explained to The Daily Meal. "There is a group of people that, up through early old age, are only a small minority, [but] who, perhaps owing to their genes, are protected against these bad effects."

So there may be some other influence at play - and Silverman warns that "we don't think increased cholesterol becomes a good thing for cognition, or [is] protective, for the oldest-old."

Conversely, he noted, the study suggests that "having high cholesterol need not be a serious source of concern" for dementia prevention.

This wouldn't be the first time science has muddied the waters on what does and does not preserve brain health.